Clinch Punch with Elastomeric Tip

ABSTRACT

A clinch joint punch includes an elastomeric tip on a distal end of an engagement section. The elastomeric tip may include a partially spherical surface or may be a cylindrical member having a planar circular engagement surface. A method of joining a clinch joint and a plurality of panels by driving a punch having an elastomeric tip into the panels. The elastomeric tip is compressed within a recess formed in the panels to mechanically interlock the panels.

TECHNICAL FIELD

This disclosure relates to punches used to form clinch joints in sheet metal or composite assemblies.

BACKGROUND

Assembly operations for joining aluminum parts, composite parts and mixed metal parts are being developed to maximize the use of lightweight parts and improve fuel economy. Currently, self-piercing rivets are used to join aluminum, composite and mixed metal part assemblies because they can provide a strong joint between adjacent parts. Self-piercing rivets add weight to the assembly and also add cost that is added to the final product.

Clinch joints are used in some applications but are not as strong as self-piercing rivet joints, particularly in the coach peel orientation. Clinch joints are lighter weight and less expensive than self-piercing rivet joints because they do not require a rivet. Clinch joints are generally not as strong or robust as self-piercing rivets because they are limited by the extent of mechanical interlock that can be achieved between the joined panels.

The above problems and challenges and others are addressed by this disclosure as summarized below.

SUMMARY

According to one aspect of this disclosure, a punch is disclosed for forming a clinch joint in a metal or composite assembly. The punch includes a body having an engagement section provided on one end of the body that terminates at a distal end. An elastomeric tip is provided on the distal end of the engagement section. The elastomeric tip engages the metal assembly in conjunction with the distal end of the engagement section to form the clinch joint.

According to other aspects of this disclosure, the distal end of the punch may be a planar circular surface and the tip may have a planar circular attachment surface that is attached to the distal end. The tip may alternatively include an end surface that is a section of a sphere. The tip may be attached with an adhesive to the distal end.

According to another aspect of this disclosure, the distal end of the punch may be a planar circular surface, and the tip may be a cylindrical member that has a planar circular attachment surface that is adhesively attached to the distal end. The tip may have a planar circular engagement surface.

According to an alternative aspect of this disclosure the punch may have a central axis and the distal end may define a receptacle that is coaxial with the central axis. The tip may include an extension that is received in the receptacle to attach the tip to the distal end. In addition, an adhesive may be applied to attach the tip to the distal end.

According to another aspect of this disclosure, a method of forming a clinch joint in a plurality of panels is disclosed. The method of forming a clinch joint includes driving a punch having an elastomeric tip into the panels to form an indentation in the panels and compresses the tip within the indentation to enhance the mechanical interlock between the panels.

According to another aspect of the method of this disclosure, the step of compressing the tip may cause the tip to expand radially outwardly within the indentation to radially expand a portion of the indentation in the panels above a base wall of the indentation.

The above aspects of this disclosure and other aspects will be described in greater detail below with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of two panels joined by a prior art clinch joint.

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is a diagrammatic, partial cross-sectional view of a clinch punch tool showing the panels disposed on a back-up die before clinching.

FIG. 4 is a diagrammatic, partial cross-sectional view of a clinch punch tool showing the panels disposed against a back-up die during clinching.

FIG. 5 is a cross-sectional view of an enhanced clinch joint.

FIG. 6 is a fragmentary cross-sectional view of a clinch joint punch having a partially spherical elastomeric tip.

FIG. 7 is a fragmentary cross-sectional view of a clinch joint punch having a cylindrical elastomeric tip.

FIG. 8 is a fragmentary cross-sectional view of a a clinch joint punch having a partially spherical elastomeric tip with an extension received in an axial bore in the punch.

DETAILED DESCRIPTION

A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention.

Referring to FIG. 1, a prior art clinch joint 10 is shown that is utilized to connect a top panel 12 to a bottom panel 14. The clinch joint 10 is formed by providing a circular recess 16 in both the top panel 12 and the bottom panel 14. The circular recess 16 includes a cylindrical side wall 18 and a base wall 20 that are formed in the top panel 12.

Referring to FIG. 2, the clinch joint 10 is shown in cross section to include an outer side wall 24 of the bottom panel 14 that is formed when the recess 16 is formed in the top panel 12. An outer interlocking surface 26 of the top panel 12 is mechanically interlocked with an inner interlocking surface 28 of the bottom panel 14.

Referring to FIG. 3, a clinch punch is generally indicated by reference numeral 30 that includes an elastomeric tip 32. The elastomeric tip 32 is provided on an engagement section 34 of the clinch punch 30. The engagement section 34 of the clinch punch 30 supports the elastomeric tip 32. Engagement section 34 may be tapered to facilitate extraction of the clinch punch 30 from the clinch joint 10 (shown in FIG. 1). The clinch punch 30 is retained within a clinch tool 36. The clinch tool 36 retains a clinch punch body 38 of the clinch punch 30.

A back-up die 40 is shown supporting the top panel 12 and bottom panel 14 on a panel support 42. A button forming surface 44 is provided within the panel support 42. The button forming surface 44 forms the bottom side of the bottom panel 14 on the opposite side of the top panel 12 that is engaged by the clinch punch 30.

Referring to FIG. 4, the clinch punch 30 is shown with the clinch tool 36 retaining the clinch punch body 38. The clinch punch 30 drives the elastomeric tip 32 and engagement section 34 into the top panel 12 that is, in turn, driven into the bottom panel 14. The panels 12, 14 are supported on the panel support 42 and the bottom panel 14 is driven into engagement with the button forming surface 44.

The elastomeric tip 32 may be formed of a high density polyurethane material, nylon material, or the like that is tough and durable yet compressible under pressure to form a radial expanded portion 46. The radial expanded portion 46 expands in a radial direction and forces the top panel 12 into the bottom panel 14. The radial expanded portion 46 of the elastomeric tip 32, shown in FIG. 4, engages the cylindrical side wall 18 and forms a portion immediately above the base wall 20 in a radially outward direction to thereby form the enhanced interlock area 48.

Referring to FIG. 5, an enhanced interlock area 48 of an enhanced clinch joint 10′ is shown having been formed in the outer interlocking surface 26 of the top panel 12 and the inner interlocking surface 28 of the bottom panel 14.

Referring to FIG. 6, one embodiment of a clinch punch 30 is partially shown to include an elastomeric tip 32. The engagement section 34 includes a planar circular surface 50 on a distal end 52. A planar circular attachment surface 54 is provided on the elastomeric tip 32. The planar circular attachment surface 54 is attached to the planar circular surface 50 by an adhesive 56. The elastomeric tip 32 has a partially spherical end surface 58, that may also be described as a section of a sphere, that initially engages the top panel 12, as explained with reference to FIG. 4.

Referring to FIG. 7, another alternative embodiment is shown that includes a planar circular end surface 60 on the elastomeric tip 32′. The elastomeric tip 32′ includes an attachment surface 54 that is adapted to be attached to the planar circular surface 50 on the distal end 52 of the engagement portion 34. An adhesive 56 is used to secure the attachment surface 54 to the planar circular surface 50.

Referring to FIG. 8, another alternative embodiment is shown that includes an elastomeric tip 32″. The clinch punch 30 has a central axis 64 and defines a receptacle 66 that extends partially into the engagement section 34 and through the surface 50. An extension 68 is provided on the elastomeric tip 32″. The elastomeric tip 32″ is retained in the receptacle 66 defined by the engagement section 34 by the resiliency of the elastomeric material forming the elastomeric tip 32″. The elastomeric tip 32″ may also be secured by an adhesive (not shown) as described with reference to FIGS. 6 and 7 above. While the elastomeric tip 32″ is illustrated with a partially spherical end surface, it should be understood that the tip could have a planar end surface as shown in FIG. 7.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention. 

What is claimed is:
 1. A punch for forming a clinch joint in a panel assembly comprising: a body; an engagement section provided on one end of the body that terminates at a distal end; and an elastomeric tip provided on the distal end of the engagement section that engages the panel assembly in conjunction with the distal end to form the clinch joint.
 2. The punch of claim 1 wherein the distal end is a planar circular surface, and wherein the tip has a planar circular attachment surface that is attached to the distal end and an end surface that is a section of a sphere.
 3. The punch of claim 2 wherein the tip is attached with an adhesive to the distal end.
 4. The punch of claim 1 wherein the distal end is a planar circular surface, and wherein the tip is a cylindrical member that has a planar circular attachment surface that is attached to the distal end and a planar circular engagement surface.
 5. The punch of claim 4 wherein the planar circular attachment surface of the tip is attached with an adhesive to the distal end.
 6. The punch of claim 1 wherein the punch has a central axis and the distal end defines a receptacle that is coaxial with the central axis, and wherein the tip includes an extension that is received in the receptacle to attach the tip to the distal end.
 7. The punch of claim 6 wherein the tip is further attached with an adhesive to the distal end.
 8. A method of forming a clinch joint in a plurality of panels comprising: driving a punch having an elastomeric tip into the panels to form a recess in the panels; and compressing the elastomeric tip within the recess to mechanically interlock the panels.
 9. The method of claim 8 wherein the recess has a base wall and, wherein the step of compressing the tip causes the tip to expand radially outwardly within the recess and into a sidewall to radially expand a portion of the sidewall of the recess in the panels.
 10. The method of claim 8 wherein the punch has a distal end that is a planar circular surface, and wherein the tip has a planar circular attachment surface that is attached to the distal end and an end surface that is a section of a sphere.
 11. The method of claim 10 wherein the tip is attached with an adhesive to the distal end.
 12. The method of claim 8 wherein the punch has a distal end that is a planar circular surface, and wherein the tip is a cylindrical member that has a planar circular attachment surface that is attached to the distal end and a planar circular engagement surface.
 13. The method of claim 12 wherein the planar circular attachment surface of the tip is attached with an adhesive to the distal end.
 14. The method of claim 8 wherein the punch has a central axis and a distal end that defines a receptacle that is coaxial with the central axis, and wherein the tip includes an extension that is received in the receptacle to attach the tip to the distal end.
 15. The method of claim 14 wherein the tip is further attached with an adhesive to the distal end. 